Particle filter for mems device

ABSTRACT

Various embodiments of the present disclosure are directed towards a microphone including a particle filter disposed between a microelectromechanical systems (MEMS) substrate and a carrier substrate. A MEMS device structure overlies the MEMS substrate. The MEMS device structure includes a diaphragm having opposing sidewalls that define a diaphragm opening. The carrier substrate underlies the MEMS substrate. The carrier substrate has opposing sidewalls that define a carrier substrate opening underlying the diaphragm opening. A filter stack is sandwiched between the carrier substrate and the MEMS substrate. The filter stack includes an upper dielectric layer, a lower dielectric layer, and a particle filter layer disposed between the upper and lower dielectric layers. The particle filter layer includes the particle filter spaced laterally between the opposing sidewalls of the carrier substrate.

BACKGROUND

Microelectromechanical systems (MEMS) devices, such as accelerometers,pressure sensors, and microphones, have found widespread use in manymodern day electronic devices. MEMS devices may have a movable part,which is used to detect a motion, and convert the motion to electricalsignal. For example, MEMS accelerometers and microphones are commonlyfound in automobiles (e.g., in airbag deployment systems), tabletcomputers, or in smart phones. A MEMS accelerometer includes a movablepart that transfer the accelerating movement to an electrical signal. Amicrophone includes a movable membrane that transfer the sound to anelectrical signal.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a cross-sectional view of some embodiments of amicroelectromechanical systems (MEMS) microphone with a particle filter.

FIGS. 2A and 2B illustrate top views of alternative embodiments of theMEMS microphone of FIG. 1.

FIG. 3 illustrates a cross-sectional view of some embodiments of amicroelectromechanical systems (MEMS) microphone with a particle filter.

FIG. 4 illustrates a cross-sectional view of some embodiments of anintegrated chip including some embodiments of the MEMS microphone ofFIG. 1 wire bonded to a complementary metal-oxide-semiconductor (CMOS)integrated circuit (IC) die.

FIGS. 5-11 illustrate cross-sectional views of some embodiments of afirst method of forming a MEMS microphone with a particle filter.

FIG. 12 illustrates a methodology in flowchart format that illustratessome embodiments of the first method of forming a MEMS microphone with aparticle filter.

FIGS. 13-20 illustrate cross-sectional views of some embodiments of asecond method of forming a MEMS microphone with a particle filter.

FIG. 21 illustrates a methodology in flowchart format that illustratessome embodiments of the second method of forming a MEMS microphone witha particle filter.

FIGS. 22-29 illustrate cross-sectional views of some embodiments of athird method of forming a MEMS microphone with a particle filter.

FIG. 30 illustrates a methodology in flowchart format that illustratessome embodiments of the third method of forming a MEMS microphone with aparticle filter.

DETAILED DESCRIPTION

The present disclosure provides many different embodiments, or examples,for implementing different features of this disclosure. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Moreover, “first”, “second”, “third”, etc. may be used herein for easeof description to distinguish between different elements of a figure ora series of figures. “first”, “second”, “third”, etc. are not intendedto be descriptive of the corresponding element. Therefore, “a firstdielectric layer” described in connection with a first figure may notnecessarily corresponding to a “first dielectric layer” described inconnection with another figure.

Microelectromechanical system (MEMS) devices used for acousticalapplications (e.g., MEMs microphones) are often housed within a packagestructure that has an opening (i.e., an inlet). The package structure isconfigured to provide protection of a MEMS device while the openingallows for sound waves to reach a cavity of the package structureholding the MEMS device. Within such a package, a MEMS device may beelectrically coupled to an application-specific integrated circuit(ASIC) disposed within the cavity of the package structure. The MEMSdevice has movable parts directly overlying the opening of the packagestructure, and a particle filter is disposed between the movable partsand the opening of the package structure. The particle filter isconfigured to prevent particles from entering the opening of the packagestructure, thereby mitigating particles that reach the movable parts.Particles interacting with the movable parts may decreases performanceof the MEMS device, by causing short circuits and/or decreasing anacoustic overload point (AOP) of the MEMS device.

One approach to fabricate a particle filter for a MEMS device is to formthe particle filter separate from fabricating the MEMS device and theASIC. For example, the MEMS device may be fabricated with moveableelements, and the ASIC may be fabricated with semiconductor devices(e.g., transistors). A package substrate may be provided to integratethe MEMS device and ASIC. A package structure opening may be formed inthe package substrate, and subsequently, a particle filter may be formedover the package structure opening. After forming the particle filter,the MEMS device is directly attached to the particle filter. Thus, themoveable elements of the MEMS device directly overlie the packagestructure opening. In some embodiments, the particle filter may bedirectly attached to the MEMS device before attaching the MEMS device tothe substrate. The direct attachment process may include utilizingalignment marks formed on the MEMS device and/or the particle filter,and/or performing a bonding process.

A problem with the aforementioned approaches is the extra processingsteps utilized to form the particle filter and directly attach theparticle filter to the MEMS device. This, in part, increases time andcosts associated with integrating the MEMS device and the ASIC on thepackage substrate. Further, during the direct attachment process, asmall thickness (e.g., less than 0.5 micrometers) of the particle filtermay result in damage and/or destruction of the particle filter, therebyreducing an ability of the particle filter to protect the moveableelements from particles. Furthermore, by virtue of the extra processingsteps utilized to from and attach the particle filter, the particlefilter and MEMS device are exposed to more particles, thus decreasingperformance of the moveable elements. In addition, the particle filtercomprises a plurality of particle filter openings and, due to processinglimitations, a diameter of the particle filter openings may each besubstantially large (e.g., about 10 micrometers or greater). This inturn may mitigate an ability to block and/or prevent particles frompassing through the particle filter openings.

The present disclosure, in some embodiments, relates to a method thatsimplifies the fabrication of a MEMS device with a particle filter. Themethod forms the particle filter and MEMS device as an integratedstructure prior to attaching the particle filter and MEMS device to apackage structure. By forming the particle filter and MEMS device as anintegrated structure, the fabrication process is simplified and damageto the particle filter is reduced. Furthermore, time and costsassociated with forming the particle filter are reduced.

As an example application, the MEMS device can be a microphone. In someembodiments, the microphone is fabricated by providing a carriersubstrate and forming a filter stack over the carrier substrate. Thefilter stack includes an upper dielectric layer, a lower dielectriclayer, and a particle filter layer disposed between the upper and lowerdielectric layers. The filter stack is patterned, thereby defining aparticle filter in the particle filter layer. A MEMS substrate is bondedto the upper dielectric layer. A MEMS device structure is formed overthe MEMS substrate. After forming the MEMS device structure, the carriersubstrate and the MEMS substrate are patterned to form openings in thecarrier and MEMs substrates. The MEMS device structure and the filterstack are patterned to form one or more moveable elements in the MEMSdevice structure and to remove the upper and lower dielectric layersfrom the particle filter. By forming the particle filter on the carriersubstrate, the carrier substrate, the upper dielectric layer, and thelower dielectric layer provide structural support for the particlefilter during fabrication of the microphone thereby reducing damage tothe particle filter. Furthermore, by removing the upper and lowerdielectric layers from the particle filter during the last patterningprocess, an exposure to particles is reduced, thereby increasingperformance of the particle filter and the moveable elements.

Referring to FIG. 1, a cross-sectional view of some embodiments of amicroelectromechanical systems (MEMS) microphone 100 with a particlefilter 106 is provided.

The MEMS microphone 100 includes a MEMS device structure 102, a MEMSsubstrate 111, a filter stack 104, and a carrier substrate 103. Thefilter stack 104 is disposed between the carrier substrate 103 and theMEMS substrate 111. The MEMS device structure 102 includes conductivewires 124 and conductive vias 122 disposed within an inter-leveldielectric (ILD) structure 120 overlying the MEMS substrate 111. TheMEMS device structure 102 further includes a first back plate 108, asecond back plate 112, and a diaphragm 110 disposed between the firstand second back plates 108, 112. The diaphragm 110 is spaced apart fromthe first back plate 108 and the second back plate 112 by one or morenon-zero distances. Further, the diaphragm 110 and the first and secondback plates 108, 112 can be electrically conductive, which forms acapacitive element. An electrical contact 114 is electrically coupled tothe diaphragm 110 and forms a first terminal for the capacitive element,an electrical contact 118 is electrically coupled to the first backplate 108 and forms a second terminal for the capacitive element, and anelectrical contact 116 is electrically coupled to the second back plate112 and forms a third terminal for the capacitive element. In someembodiments, the second terminal and the third terminal are electricallycoupled together. In some embodiments, the electrical coupling isachieved through the conductive wires 124 and the conductive vias 122.

The diaphragm 110 includes one or more diaphragm openings 109 and may beanchored by the ILD structure 120 at multiple points. Anchoring thediaphragm 110 at the multiple points allows a boundary of the diaphragm110 to be fixed relative to the first and second back plates 108, 112.The diaphragm 110 is deformable by energy of sound waves to make thediaphragm 110 bend towards or away from the first back plate 108 and/orthe second back plate 112, as the sound waves exert pressure on thediaphragm 110 through a carrier substrate opening 101 in the carriersubstrate 103. The carrier substrate 103 has sidewalls defining thecarrier substrate opening 101 and the MEMS substrate 111 has sidewallsdefining a MEMS opening 111 o. In some embodiments, a first width w₁extending between sidewalls defining outermost openings of the particlefilter 106 is less than a second width w₂ of the sidewalls of thecarrier substrate 103 defining the carrier substrate opening 101. Thefirst and second back plates 108, 112 each comprise a plurality ofopenings by which air may pass through. There is an air volume space 113between the first and second back plates 108, 112. The air volume space113 is above and below the diaphragm 110. Air can get out of or get intothe air volume space 113 through air passage ways formed by theplurality of openings in each of the first and second back plates 108,112, and/or through the one or more diaphragm openings 109 of thediaphragm 110. The air travels out of or into the air volume space 113as the diaphragm 110 bends towards or away from the first back plate 108and/or the second back plate 112. The bending movement of the diaphragm110 relative to the first back plate 108 and/or the second back plate112 by the sound waves changes the capacitance of the capacitive elementbetween the diaphragm 110 and the first and/or second back plates 108,112. Such change of the capacitance can be measured with the electricalcontacts 114, 116, 118.

As the air travels through the carrier substrate opening 101 in thecarrier substrate 103 to the air volume space 113, it passes through theparticle filter 106. In some embodiments, the particle filter 106 is apart of the filter stack 104. The filter stack 104 comprises a lowerdielectric layer 104 a, a particle filter layer 104 b, and an upperdielectric layer 104 c. In some embodiments, the lower dielectric layer104 a may comprise an oxide (e.g., silicon dioxide), the particle filterlayer 104 b may comprise a nitride (e.g., silicon nitride), and theupper dielectric layer 104 c may comprise an oxide (e.g., silicondioxide). The particle filter 106 is a segment of the particle filterlayer 104 b between the carrier substrate opening 101 and MEMS opening111 o. The particle filter 106 comprises a plurality of filter openings107 configured to pass air from the carrier substrate opening 101 to theair volume space 113. As the air passes from the carrier substrateopening 101 to the air volume space 113, the particle filter 106 isconfigured to block and/or remove particles from the air that mayadversely affect the movement of the diaphragm 110. In some embodiments,the particles may, for example, be by-products from and/or chemicalsused in a laser dicing process implemented to form the MEMS microphone100. The particles interacting with the diaphragm 110 may decrease aperformance of the MEMS microphone 100 by, for example, causing shortcircuits (e.g., between the first and second back plates 108, 112 andthe diaphragm 110) and/or decreasing an acoustic overload point (AOP) ofthe MEMS microphone 100.

By disposing the particle filter 106 over the carrier substrate 103, atime and costs associated with fabricating the MEMS microphone 100 isreduced. Additionally, the carrier substrate 103, the upper dielectriclayer 104 c, and the lower dielectric layer 104 a may provide structuralsupport for the particle filter 106 during fabrication of the MEMSmicrophone 100. For example, during a fabrication of the MEMS microphone100, the filter stack 104 may be formed over the carrier substrate 103,and subsequently the upper dielectric layer 104 c may be bonded to theMEMS substrate 111. The carrier substrate 103, the upper dielectriclayer 104 c, and the lower dielectric layer 104 a prevent damage ordestruction to the particle filter layer 104 b during the aforementionedbonding process. Further, by disposing the particle filter layer 104 bbetween the upper and lower dielectric layers 104 c, 104 a, an exposureof particles directly to the particle filter 106 during fabrication ofthe MEMS microphone 100 may be reduced, thereby increasing an enduranceand reliability of the MEMS microphone 100.

Referring to FIG. 2A, a top view 200 a of some alternative embodimentsof the particle filter 106 of FIG. 1 along the line A-A′ is provided.

As seen in FIG. 2A, the plurality of filter openings 107 disposed in theparticle filter layer 104 b each have a circular and/or ellipticalshape. The plurality of filter openings 107 may be arranged as an arraycomprising columns and rows across the carrier substrate opening 101 ofFIG. 1. The particle filter 106 is configured to block and/or removeparticles (e.g., by a shape/size of the filter openings 107 and/or amaterial of the particle filter layer 104 b) from air that passes from afirst surface of the particle filter 106 to an opposite second surfaceof the particle filter 106.

In some embodiments, the filter openings 107 each have a diameter d thatmay, for example, be within a range of about 3 to 10 micrometers. Insome embodiments, if the diameter d is less than about 3 micrometers,then an ability to pass air from the first surface of the particlefilter 106 to the opposite second surface of that particle filter 106may be mitigated, thereby decreasing a performance of the MEMS devicestructure 102. In further embodiments, if the diameter d is greater thanabout 10 micrometers, then an ability of the particle filter 106 toblock and/or remove particles from the air that passes through theparticle filter 106 may be reduced. For example, the particle filteropenings 107 may be larger than the particles, such that the particlesmay pass through the particle filter openings and adversely affect themovement of the diaphragm (110 of FIG. 1).

Referring to FIG. 2B, a top view 200 b of some alternative embodimentsof the particle filter 106 of FIG. 1 along the line A-A′ is provided.

As seen in FIG. 2B, the plurality of filter openings 107 disposed in theparticle filter layer 104 b each have a polygon shape. The polygon shapemay be any polygon, for example, a triangle, a rectangle, a pentagon, ahexagon, etc. The plurality of filter openings 107 may be arranged as anarray comprising columns and rows across the carrier substrate opening101 of FIG. 1. The particle filter 106 is configured to block and/orremove particles (e.g., by a shape/size of the filter openings 107and/or a material of the particle filter layer 104 b) from air thatpasses from a first surface of the particle filter 106 to an oppositesecond surface of the particle filter 106.

In some embodiments, one or more sides of each filter opening 107 have alength len that may, for example, be within a range of about 3 to 10micrometers. In some embodiments, if the length len is less than about 3micrometers, then an ability to pass air from the first surface of theparticle filter 106 to the opposite second surface of that particlefilter 106 may be mitigated, thereby decreasing a performance of theMEMS device structure 102. In further embodiments, if the length len isgreater than about 10 micrometers, then an ability of the particlefilter 106 to block and/or remove particles from the air that passesthrough the particle filter 106 may be reduced. For example, theparticle filter openings 107 may be larger than the particles, such thatthe particles may pass through the particle filter openings andadversely affect the movement of the diaphragm (110 of FIG. 1).

Referring to FIG. 3, a cross-sectional view of a MEMS microphone 300corresponding to some alternative embodiments of the MEMS microphone 100of FIG. 1 is provided.

In some embodiments, the particle filter layer 104 b comprises a lowerparticle filter layer 302, a middle particle filter layer 304, and anupper particle filter layer 306. The lower particle filter layer 302may, for example, be or comprise silicon, a nitride, silicon nitride, orthe like and/or have a thickness within a range of about 0.2 to 1micrometer. The middle particle filter layer 304 may, for example, be orcomprise polysilicon, un-doped polysilicon, or the like and/or have athickness within a range of about 0.2 to 1 micrometer. The upperparticle filter layer 306 may, for example, be or comprise silicon, anitride, silicon nitride, or the like and/or have a thickness within arange of about 0.2 to 1 micrometer. In some embodiments, the layerswithin the particle filter layer 104 b may each have a substantiallysame thickness. In further embodiments, the lower particle filter layer302 and the upper particle filter layer 306 may comprise a same material(e.g., silicon nitride). In some embodiments, the particle filter layer104 b including a polysilicon layer (e.g., the middle particle filterlayer 304) disposed between two silicon nitride layers (e.g., the lowerand upper particle filter layers 302, 306) will decrease a stressinduced upon the particle filter 106, thereby increasing a structuralintegrity and reliability of the particle filter 106.

Referring to FIG. 4, a cross-sectional view of some embodiments of anintegrated chip 400 including some alternative embodiments of the MEMSmicrophone 100 of FIG. 1 wire bonded to a complementarymetal-oxide-semiconductor (CMOS) integrated circuit (IC) die 402 isprovided.

The integrated chip 400 includes the MEMS microphone 100 laterallyadjacent to the CMOS IC die 402 and disposed within a cavity 403. Insome embodiments, the MEMS substrate 111 of the MEMS microphone 100includes pillar structures 420 configured to increase a structuralintegrity of the MEMS microphone 100. In some embodiments, the CMOS ICdie 402 may be an application-specific integrated circuit (ASIC). Insome embodiments, the cavity 403 is defined by inner sidewalls of apackage 401. The package 401 includes a front-side structure 401 a andan enclosure structure 401 b. The CMOS IC die 402 and the MEMSmicrophone 100 are disposed on the front-side structure 401 a. In someembodiments, an opening (i.e., inlet) to the package 401 may be thecarrier substrate opening 101 of the MEMS microphone 100, such that anyair entering or leaving the cavity 403 passes through the particlefilter 106.

The CMOS IC die 402 includes a back-end-of-line (BEOL) metallizationstack 412 overlying a CMOS substrate 410. An inter-level dielectric(ILD) structure 413 overlies the CMOS substrate 410. The CMOS substrate410 and the ILD structure 413 include electronic components such astransistors 408, and/or other electric components (not shown), such asone or more capacitors, resistors, inductors, or diodes. The CMOSsubstrate 410 may, for example, be or comprise a bulk semiconductorsubstrate or a silicon-on-insulator (SOI) substrate. The BEOLmetallization stack 412 includes the ILD structure 413, interconnectwires 416, and interconnect vias 414. The ILD structure 413 may compriseone or more stacked ILD layers, which respectively comprise a low-kdielectric (i.e., a dielectric material with a dielectric constant lessthan about 3.9), and oxide, or the like. The interconnect vias and wires414, 416 may, for example, respectively be or comprise a conductivematerial, such as aluminum, copper, tungsten, or the like.

A solder ball 404 is disposed over each electrical contact 114, 116,118. The solder balls 404 provide contact points for a plurality of bondwires 406. A bond pad 418 overlies a top layer of interconnect wires 416and provides a wire bonding location for the bond wires 406. Thetransistors 408 are electrically coupled to the electrical contacts 114,116, 118 by way of the BEOL metallization stack 412, the bond wires 406,and the bond pads 418. The transistors 408 may be configured to receivesignals from the first back plate 108, the second back plate 112, and/orthe diaphragm 110.

FIGS. 5-11 illustrate cross-sectional views 500-1100 of some embodimentsof a first method of forming a MEMS microphone with a particle filteraccording to the present disclosure. Although the cross-sectional views500-1100 shown in FIGS. 5-11 are described with reference to a method,it will be appreciated that the structures shown in FIGS. 5-11 are notlimited to the method but rather may stand alone separate of the method.Furthermore, although FIGS. 5-11 are described as a series of acts, itwill be appreciated that these acts are not limiting in that the orderof the acts can be altered in other embodiments, and the methodsdisclosed are also applicable to other structures. In other embodiments,some acts that are illustrated and/or described may be omitted in wholeor in part.

A shown in cross-sectional view 500 of FIG. 5, a carrier substrate 103is provided. In some embodiments, the carrier substrate 103 may be, forexample, a bulk substrate (e.g., a bulk silicon substrate), asilicon-on-insulator (SOI) substrate, or some other suitable substrateand/or may have an initial thickness T_(i) within a range ofapproximately 250 to 725 micrometers. A filter stack 104 is formed overthe carrier substrate 103. The filter stack 104 includes a lowerdielectric layer 104 a, a particle filter layer 104 b, and an upperdielectric layer 104 c. In some embodiments, a process for forming thefilter stack 104 includes: depositing the lower dielectric layer 104 aover the carrier substrate 103 and subsequently performing a firstannealing process; depositing the particle filter layer 104 b over thelower dielectric layer 104 a and subsequently performing a secondannealing process; and depositing an upper dielectric layer 104 c overthe particle filter layer 104 b and subsequently performing a thirdannealing process. In some embodiments, the aforementioned layers of thefilter stack 104 may respectively, for example, be deposited and/orgrown by chemical vapor deposition (CVD), physical vapor deposition(PVD), atomic layer deposition (ALD), thermal oxidation, or anothersuitable deposition process.

In some embodiments, the lower dielectric layer 104 a may, for example,be or comprise an oxide, such as silicon dioxide, or another dielectricmaterial formed to a thickness within a range of about 0.5 to 10micrometers. In some embodiments, the particle filter layer 104 b may,for example, be or comprise a nitride, such as silicon nitride, or thelike formed to a thickness within a range of about 0.1 to 3 micrometers.In some embodiments, the upper dielectric layer 104 c may, for example,be or comprise an oxide, such as silicon dioxide, or another dielectricmaterial formed to a thickness within a range of about 0.5 to 10micrometers. In further embodiments, the lower dielectric layer 104 aand the upper dielectric layer 104 c may be or comprise the samematerial with approximately the same thickness.

Also shown in FIG. 5, the filter stack 104 is etched, thereby defining aplurality of filter openings 107 and a particle filter 106. In someembodiments, the etching process includes: forming a masking layer (notshown) over the upper dielectric layer 104 c, exposing unmasked regionsof the upper dielectric layer 104 c to one or more etchants, andperforming a removal process to remove the masking layer.

The carrier substrate 103, the upper dielectric layer 104 c, and thelower dielectric layer 104 a each provide structural support for theparticle filter 106 and/or the particle filter layer 104 b duringsubsequent processing steps. This, in part, reduces and/or eliminatesdamage to the particle filter layer 104 b and/or particle filter 106during fabrication.

As shown in cross-sectional view 600 of FIG. 6, a MEMS substrate 111 isprovided and subsequently bonded to the upper dielectric layer 104 c. Insome embodiments, the bonding process may, for example, be a fusionbonding process, or another suitable bonding process. In someembodiments, the MEMS substrate 111 may be, for example, a bulksubstrate (e.g., a bulk silicon substrate), a silicon-on-insulator (SOI)substrate, or some other suitable substrate with an initial thicknessT_(r). After performing the bonding process, a thinning process isperformed on the MEMS substrate 111 to reduce the initial thicknessT_(r) of the MEMS substrate 111 to a thickness T_(ms). In someembodiments, the thickness T_(ms) is within a range of about 10 to 200micrometers. In some embodiments, the thinning process is performed by amechanical grinding process, a chemical mechanical polish (CMP), someother thinning process, or any combination of the foregoing. Forexample, the thinning process may be performed wholly by a mechanicalgrinding process.

As shown in cross-sectional view 700 of FIG. 7, a MEMS device structure102 is formed over the MEMS substrate 111. The MEMS device structure 102includes conductive wires 124, conductive vias 122, an inter-leveldielectric (ILD) structure 120, a first back plate 108, a second backplate 112, and a diaphragm 110 disposed between the first and secondback plates 108, 112. The ILD structure 120 may be one or moredielectric layers. The one or more dielectric layers may, for example,be or comprise an oxide, such as silicon dioxide, or another suitableoxide. In some embodiments, a process for forming the MEMS devicestructure 102 includes forming a bottommost layer of the conductive vias122 by a single damascene process, and subsequently forming a bottommostlayer of the conductive wires 124 by the single damascene process.Further, in some embodiments, the process comprises forming remaininglayers of the conductive vias and wires 122, 124 by repeatedlyperforming a dual damascene process. Additionally, the first back plate108, the second back plate 112, and the diaphragm 110 may be formedduring the dual damascene process or the single damascene process of acorresponding layer of the conductive wires 124. For example, the firstback plate 108 may be formed concurrently with the single damasceneprocess used to form the bottommost layer of the conductive wires 124.In another example, the first back plate 108, the second back plate 112,and the diaphragm 110 may each be formed by depositing a layer ofpolysilicon (e.g., by CVD, PVD, or another suitable deposition process),patterning the layer of polysilicon according to a masking layer (notshown), and performing a removal process to remove the masking layer.

In some embodiments, the single damascene process comprises depositing adielectric layer, patterning the dielectric layer with openings for asingle layer of conductive features (e.g., a layer of vias, wires, aback plate, and/or a diaphragm), and filling the openings withconductive material (e.g., polysilicon) to form the single layer ofconductive features. The dielectric layer may, for example, correspondto the one or more dielectric layers in the ILD structure 120. In someembodiments, the dual damascene process comprises depositing adielectric layer, patterning the dielectric layer with openings for twolayers of conductive features (e.g., a layer of vias and a layer ofwires, back plate, and/or a diaphragm), and filling the openings withconductive material (e.g., polysilicon) to form the two layers ofconductive features. In some embodiments, the conductive wires 124, theconductive vias 122, the first back plate 108, the second back plate112, and the diaphragm 110 may, for example, respectively comprisepolysilicon, or another suitable conductive material.

Also as shown in FIG. 7, the process for forming the MEMS devicestructure 102 further includes forming electrical contacts 114, 116,118. In some embodiments, a process for forming the aforementionedelectrical contacts includes: forming a masking layer (not shown) overthe ILD structure 120; patterning the ILD structure 120 according to themasking layer; and depositing the electrical contacts 114, 116, 118 overthe ILD structure 120. The aforementioned electrical contacts may, forexample, be deposited and/or grown by electroless plating, sputtering,electroplating, or another suitable deposition process. In someembodiments, the electrical contacts 114, 116, 118 may, for example,respectively be or comprise gold, nickel, or the like.

As shown in cross-sectional view 800 of FIG. 8, a thinning process isperformed on the carrier substrate 103 to reduce an initial thicknessT_(i) of the carrier substrate 103 to a thickness T_(cs). In someembodiments, the thickness T_(cs) is within a range of about 200 to 400micrometers. In some embodiments, the thinning process is performed by amechanical grinding process, a chemical mechanical polish (CMP), someother thinning process, or any combination of the foregoing. Forexample, the thinning process may be performed wholly by a mechanicalgrinding process. After performing the thinning process, a lower maskinglayer 802 is formed on a bottom surface of the carrier substrate 103 andan upper masking layer 804 is formed over the ILD structure 120. In someembodiments, the lower masking layer 802 and/or the upper masking layer804 may, for example, respectively be or comprise a photoresist, a hardmask layer, or the like. The lower masking layer 802 and the uppermasking layer 804 respectively have a plurality of sidewalls defining aplurality of openings.

As shown in cross-sectional view 900 of FIG. 9, a first patterningprocess is performed on the carrier substrate 103 and the MEMS substrate111 according to the lower masking layer 802. In some embodiments, thefirst patterning process includes performing a dry etching process, suchas a plasma etching process and/or a deep reactive-ion etching (DRIE)process. The first patterning process defines the carrier substrateopening 101 directly underlying the particle filter 106. Additionally,the first patterning process defines a plurality of pillars 902 from theMEMS substrate 111. In some embodiments, after the first patterningprocess, the MEMS substrate 111 comprises a plurality of openings thatcorrespond to a shape of the plurality of the filter openings 107 of theparticle filter 106.

As shown in cross-sectional view 1000 of FIG. 10, a second patterningprocess is performed on the carrier substrate 103 and the MEMS substrate111 according to the lower masking layer 802. In some embodiments, thesecond patterning process includes performing a wet etching process,such as an isotropic etching process and/or a dry etching process. Thesecond patterning process may include exposing the carrier substrate 103and/or the MEMS substrate 111 to one or more etchants, such as, forexample, xenon difluoride (XeF₂). The second patterning process removesthe plurality of pillars (902 of FIG. 9) and expands the carriersubstrate opening 101.

As shown in cross-sectional view 1100 of FIG. 11, a third patterningprocess is performed on the structure of FIG. 10 according to the lowermasking layer (802 of FIG. 10) and the upper masking layer (804 of FIG.10). In some embodiments, the third patterning process includesperforming a wet etching process. In some embodiments, the thirdpatterning process includes exposing the structure of FIG. 10 to one ormore etchants. The third patterning process removes a portion of the ILDstructure 120 thereby defining the air volume space 113. Further, thethird patterning process removes the lower dielectric layer 104 a from abottom surface of the particle filter 106 and removes the upperdielectric layer 104 c from a top surface of the particle filter 106.After performing the third patterning process, a removal process isperformed to remove the lower and upper masking layers (802, 804 of FIG.10).

FIG. 12 illustrates a first method 1200 of forming a MEMS microphonewith a particle filter in accordance with some embodiments. Although thefirst method 1200 is illustrated and/or described as a series of acts orevents, it will be appreciated that the method is not limited to theillustrated ordering or acts. Thus, in some embodiments, the acts may becarried out in different orders than illustrated, and/or may be carriedout concurrently. Further, in some embodiments, the illustrated acts orevents may be subdivided into multiple acts or events, which may becarried out at separate times or concurrently with other acts orsub-acts. In some embodiments, some illustrated acts or events may beomitted, and other un-illustrated acts or events may be included.

At act 1202, a carrier substrate is provided. FIG. 5 illustrates across-sectional view 500 corresponding to some embodiments of act 1202.

At act 1204 a filter stack is formed over the carrier substrate. Thefilter stack includes an upper dielectric layer, a particle filterlayer, and a lower dielectric layer, the particle filter layer isdisposed between the upper and lower dielectric layers. FIG. 5illustrates a cross-sectional view 500 corresponding to some embodimentsof act 1204.

At act 1206, an etching process is performed on the filter stack,thereby defining a particle filter in the particle filter layer. FIG. 5illustrates a cross-sectional view 500 corresponding to some embodimentsof act 1206.

At act 1208, a MEMS substrate is bonded to the upper dielectric layer.FIG. 6 illustrates a cross-sectional view 600 corresponding to someembodiments of act 1208.

At act 1210, a MEMS structure is formed over the MEMS substrate. TheMEMS structure includes a first back plate, a second back plate, and adiaphragm disposed between the first and second back plates. FIG. 7illustrates a cross-sectional view 700 corresponding to some embodimentsof act 1210.

At act 1212, a dry etching process is performed on the carrier and MEMSsubstrates, thereby defining an opening in the carrier substrate anddefining pillars in the MEMS substrate. FIG. 9 illustrates across-sectional view 900 corresponding to some embodiments of act 1212.

At act 1214, a wet etching process is performed on the carrier and MEMSsubstrates, thereby expanding the opening in the carrier substrate andremoving the pillars. FIG. 10 illustrates a cross-sectional view 1000corresponding to some embodiments of act 1214.

At act 1216, an etching process is performed on the MEMS structure andthe filter stack, thereby defining an air volume space around the firstback plate, second back plate, and the diaphragm. The etching processremoves the upper and lower dielectric layers from the particle filter.FIG. 11 illustrates a cross-sectional view 1100 corresponding to someembodiments of act 1216.

FIGS. 13-20 illustrate cross-sectional views 1300-2000 of someembodiments of a second method of forming a MEMS microphone with aparticle filter according to the present disclosure. Although thecross-sectional views 1300-2000 shown in FIGS. 13-20 are described withreference to a method, it will be appreciated that the structures shownin FIGS. 13-20 are not limited to the method but rather may stand aloneseparate of the method. Furthermore, although FIGS. 13-20 are describedas a series of acts, it will be appreciated that these acts are notlimiting in that the order of the acts can be altered in otherembodiments, and the methods disclosed are also applicable to otherstructures. In other embodiments, some acts that are illustrated and/ordescribed may be omitted in whole or in part.

A shown in cross-sectional view 1300 of FIG. 13, a carrier substrate 103is provided. In some embodiments, the carrier substrate 103 may be, forexample, a bulk substrate (e.g., a bulk silicon substrate), asilicon-on-insulator (SOI) substrate, or some other suitable substrateand/or may have an initial thickness T_(i) within a range ofapproximately 250 to 725 micrometers. A filter stack 104 is formed overthe carrier substrate 103. The filter stack 104 includes a lowerdielectric layer 104 a, a particle filter layer 104 b, and an upperdielectric layer 104 c. In some embodiments, a process for forming thefilter stack 104 includes: depositing the lower dielectric layer 104 aover the carrier substrate 103 and subsequently performing a firstannealing process; depositing the particle filter layer 104 b over thelower dielectric layer 104 a and subsequently performing a secondannealing process; and depositing an upper dielectric layer 104 c overthe particle filter layer 104 b and subsequently performing a thirdannealing process. In some embodiments, the aforementioned layers of thefilter stack 104 may respectively, for example, be deposited and/orgrown by chemical vapor deposition (CVD), physical vapor deposition(PVD), atomic layer deposition (ALD), thermal oxidation, or anothersuitable deposition process. In some embodiments, the lower dielectriclayer 104 a may, for example, be or comprise an oxide, such as silicondioxide, or another dielectric material formed to a thickness within arange of about 0.5 to 10 micrometers. In some embodiments, the particlefilter layer 104 b may, for example, be or comprise a nitride, such assilicon nitride, or the like formed to a thickness within a range ofabout 0.1 to 3 micrometers. In some embodiments, the upper dielectriclayer 104 c may, for example, be or comprise an oxide, such as silicondioxide, or another dielectric material formed to a thickness within arange of about 0.5 to 10 micrometers. In further embodiments, the lowerdielectric layer 104 a and the upper dielectric layer 104 c may be orcomprise the same material with the approximately same thickness.

As shown in cross-sectional view 1400 of FIG. 14, a MEMS substrate 111is provided and subsequently bonded to the upper dielectric layer 104 c.In some embodiments, the bonding process may, for example, be a fusionbonding process, or another suitable bonding process. In someembodiments, the MEMS substrate 111 may be, for example, a bulksubstrate (e.g., a bulk silicon substrate), a silicon-on-insulator (SOI)substrate, or some other suitable substrate with an initial thicknessT_(r). After performing the bonding process, a thinning process isperformed on the MEMS substrate 111 to reduce the initial thicknessT_(r) of the MEMS substrate 111 to a thickness T_(ms). In someembodiments, the thickness T_(ms) is within a range of about 10 to 200micrometers. In some embodiments, the thinning process is performed by amechanical grinding process, a chemical mechanical polish (CMP), someother thinning process, or any combination of the foregoing. Forexample, the thinning process may be performed wholly by a mechanicalgrinding process.

As shown in cross-sectional view 1500 of FIG. 15, a MEMS devicestructure 102 is formed over the MEMS substrate 111. The MEMS devicestructure 102 includes conductive wires 124, conductive vias 122, aninter-level dielectric (ILD) structure 120, a first back plate 108, asecond back plate 112, and a diaphragm 110 disposed between the firstand second back plates 108, 112. The ILD structure 120 may be one ormore dielectric layers. In some embodiments, the MEMS device structure102 is formed as illustrated and/or described in FIG. 7.

As shown in cross-sectional view 1600 of FIG. 16, a thinning process isperformed on the carrier substrate 103 to reduce an initial thicknessT_(i) of the carrier substrate 103 to a thickness T_(cs). In someembodiments, the thickness T_(cs) is within a range of about 200 to 400micrometers. In some embodiments, the thinning process is performed by amechanical grinding process, a chemical mechanical polish (CMP), someother thinning process, or any combination of the foregoing. Forexample, the thinning process may be performed wholly by a mechanicalgrinding process. After performing the thinning process, a lower maskinglayer 802 is formed on a bottom surface of the carrier substrate 103 andan upper masking layer 804 is formed over the ILD structure 120. In someembodiments, the lower masking layer 802 and/or the upper masking layer804 may, for example, respectively be or comprise a photoresist, a hardmask layer, or the like. The lower masking layer 802 and the uppermasking layer 804 respectively have a plurality of sidewalls defining aplurality of openings.

As shown in cross-sectional view 1700 of FIG. 17, a first patterningprocess is performed on the carrier substrate 103 according to the lowermasking layer 802. In some embodiments, the first patterning processincludes performing a dry etching process, such as a plasma etchingprocess and/or a deep reactive-ion etching (DRIE) process. The firstpatterning process defines the carrier substrate opening 101 directlyunderlying the filter stack 104 and exposes a bottom surface of thelower dielectric layer 104 a. In further embodiments, after performingthe first patterning process, a removal process is performed to removethe lower masking layer 802 (not shown).

As shown in cross-sectional view 1800 of FIG. 18, another lower maskinglayer 1802 is formed over the carrier substrate 103 and the bottomsurface of the lower dielectric layer 104 a. In some embodiments, theanother lower masking layer 1802 protects the carrier substrate 103 fromsubsequent etching processes. After forming the another lower maskinglayer 1802, a second patterning process is performed on the filter stack104 and the MEMS substrate 111. This, in part, defines a plurality ofpillars 902 in the MEMS substrate 111 and defines a particle filter 106in the particle filter layer 104 b. In some embodiments, the secondpatterning process includes performing a first dry etching process onthe filter stack 104, thereby exposing unmasked portions of the filterstack 104 to one or more first etchants. The second patterning processfurther includes performing a second dry etching process on the MEMSsubstrate 111, thereby exposing unmasked portions of the MEMS substrateto one or more second etchants. In some embodiments, the one or morefirst etchants are different than the one or more second etchants.Further, the first dry etching process defines the plurality of filteropenings 107 of the particle filter 106.

As shown in cross-sectional view 1900 of FIG. 19, a third patterningprocess is performed on the MEMS substrate 111. In some embodiments, thethird patterning process includes performing a wet etching process, suchas an isotropic etching process and/or a dry etching process. The thirdpatterning process may include exposing the MEMS substrate 111 to one ormore etchants, such as, for example, xenon difluoride (XeF₂). The thirdpatterning process removes the plurality of pillars (902 of FIG. 18).

As shown in cross-sectional view 2000 of FIG. 20, a fourth patterningprocess is performed on the structure of FIG. 19. In some embodiments,the fourth patterning process includes performing a wet etching processand exposing the structure of FIG. 19 to one or more etchants. Thefourth patterning removes a portion of the ILD structure 120 therebydefining the air volume space 113. Further, the fourth patterningprocess removes the lower dielectric layer 104 a from a bottom surfaceof the particle filter 106 and removes the upper dielectric layer 104 cfrom a top surface of the particle filter 106. After performing thefourth patterning process, a removal process is performed to remove theupper masking layer (804 of FIG. 19) and the another lower masking layer(1802 of FIG. 19).

FIG. 21 illustrates a second method 2100 of forming a MEMS microphonewith a particle filter in accordance with some embodiments. Although thesecond method 2100 is illustrated and/or described as a series of actsor events, it will be appreciated that the method is not limited to theillustrated ordering or acts. Thus, in some embodiments, the acts may becarried out in different orders than illustrated, and/or may be carriedout concurrently. Further, in some embodiments, the illustrated acts orevents may be subdivided into multiple acts or events, which may becarried out at separate times or concurrently with other acts orsub-acts. In some embodiments, some illustrated acts or events may beomitted, and other un-illustrated acts or events may be included.

At act 2102, a carrier substrate is provided. FIG. 13 illustrates across-sectional view 1300 corresponding to some embodiments of act 2102.

At act 2104 a filter stack is formed over the carrier substrate. Thefilter stack includes an upper dielectric layer, a particle filterlayer, and a lower dielectric layer, the particle filter layer isdisposed between the upper and lower dielectric layers. FIG. 13illustrates a cross-sectional view 1300 corresponding to someembodiments of act 2104.

At act 2106, a MEMS substrate is bonded to the upper dielectric layer.FIG. 14 illustrates a cross-sectional view 1400 corresponding to someembodiments of act 2106.

At act 2108, a MEMS structure is formed over the MEMS substrate. TheMEMS structure includes a first back plate, a second back plate, and adiaphragm disposed between the first and second back plates. FIG. 15illustrates a cross-sectional view 1500 corresponding to someembodiments of act 2108.

At act 2110, a dry etching process is performed on the carriersubstrate, thereby defining an opening in the carrier substrate andexposing a bottom surface of the lower dielectric layer. FIG. 17illustrates a cross-sectional view 1700 corresponding to someembodiments of act 2110.

At act 2112, a dry etching process is performed on the MEMS substrateand the filter stack, thereby defining a particle filter in the particlefilter layer and defining a plurality of pillars in the MEMS substrate.FIG. 18 illustrates a cross-sectional view 1800 corresponding to someembodiments of act 2112.

At act 2114, a wet etching process is performed on the MEMS substrate,thereby removing the plurality of pillars. FIG. 19 illustrates across-sectional view 1900 corresponding to some embodiments of act 2114.

At act 2116, an etching process is performed on the MEMS structure andthe filter stack, thereby defining an air volume space around the firstback plate, second back plate, and the diaphragm. The etching processremoves the upper and lower dielectric layers from the particle filter.FIG. 20 illustrates a cross-sectional view 2000 corresponding to someembodiments of act 2116.

FIGS. 22-29 illustrate cross-sectional views 2200-2900 of someembodiments of a third method of forming a MEMS microphone with aparticle filter according to the present disclosure. Although thecross-sectional views 2200-2900 shown in FIGS. 22-29 are described withreference to a method, it will be appreciated that the structures shownin FIGS. 22-29 are not limited to the method but rather may stand aloneseparate of the method. Furthermore, although FIGS. 22-29 are describedas a series of acts, it will be appreciated that these acts are notlimiting in that the order of the acts can be altered in otherembodiments, and the methods disclosed are also applicable to otherstructures. In other embodiments, some acts that are illustrated and/ordescribed may be omitted in whole or in part.

As shown in cross-sectional view 2200 of FIG. 22, a MEMS substrate 111is provided and a MEMS device structure 102 is formed over the MEMSsubstrate 111. The MEMS device structure 102 includes conductive wires124, conductive vias 122, electrical contacts 114, 116, 118, aninter-level dielectric (ILD) structure 120, a first back plate 108, asecond back plate 112, and a diaphragm 110 disposed between the firstand second back plates 108, 112. In some embodiments, the MEMS devicestructure 102 is formed as illustrated and/or described in FIG. 7. TheMEMS substrate 111 may be, for example, a bulk substrate (e.g., a bulksilicon substrate), a silicon-on-insulator (SOI) substrate, or someother suitable substrate with an initial thickness T_(r).

As shown in cross-sectional view 2300 of FIG. 23, an adhesive bondinglayer 2302 and a sacrificial substrate 2304 are bonded to the ILDstructure 120 of the MEMS device structure 102. In some embodiments, thebonding process is a fusion bonding process, or another suitable bondingprocess and/or may include reaching a maximum temperature within a rangeof 200 to 300 degrees Celsius. The sacrificial substrate 2304 isconfigured to increase a structural integrity of the MEMS devicestructure 102 and/or the MEMS substrate 111 during subsequent processingsteps (e.g., the thinning process of FIG. 24 and/or the bonding processof FIG. 26).

As shown in cross-sectional view 2400 of FIG. 24, a thinning process isperformed on the MEMS substrate 111 to reduce the initial thicknessT_(r) of the MEMS substrate 111 to a thickness T_(ms). In someembodiments, the thickness T_(ms) is within a range of about 10 to 200micrometers. In some embodiments, the thinning process is performed by amechanical grinding process, a chemical mechanical polish (CMP), someother thinning process, or any combination of the foregoing. Forexample, the thinning process may be performed wholly by a mechanicalgrinding process. After performing the thinning process, the MEMSsubstrate 111 is patterned to define a plurality of pillars 2402 in theMEMS substrate 111. In some embodiments, the patterning processincludes: forming a masking layer over a back surface of the MEMSsubstrate 111 (not shown); exposing unmasked regions of the MEMSsubstrate 111 to one or more etchants, thereby defining the pillars2402; and performing a removal process to remove the masking layer. Theplurality of pillars 2402 are configured to further increase astructural integrity of the MEMS substrate 111 during subsequentprocessing steps (e.g., the bonding process of FIG. 26).

As shown in cross-sectional view 2500 of FIG. 25, a carrier substrate103 is provided. In some embodiments, the carrier substrate 103 may be,for example, a bulk substrate (e.g., a bulk silicon substrate), asilicon-on-insulator (SOI) substrate, or some other suitable substrateand/or may have an initial thickness T_(i) within a range ofapproximately 250 to 725 micrometers. A filter stack 104 is formed overthe carrier substrate 103. The filter stack 104 includes a lowerdielectric layer 104 a, a particle filter layer 104 b, and an upperdielectric layer 104 c. In some embodiments, the filter stack 104 isformed as illustrated and/or described in FIG. 5.

Also shown in FIG. 25, the filter stack 104 is etched, thereby defininga plurality of filter openings 107 and a particle filter 106. In someembodiments, the etching process includes: forming a masking layer (notshown) over the upper dielectric layer 104 c, exposing unmasked regionsof the upper dielectric layer 104 c to one or more etchants, andperforming a removal process to remove the masking layer.

As shown in cross-sectional view 2600 of FIG. 26, The MEMS substrate 111is bonded to the upper dielectric layer 104 c. In some embodiments, thebonding process may, for example, be a fusion bonding process, oranother suitable bonding process. After performing the bonding process,a thinning process is performed on the carrier substrate 103 to reducean initial thickness T_(i) of the carrier substrate 103 to a thicknessT_(cs). In some embodiments, the thickness T_(cs) is within a range ofabout 200 to 400 micrometers. In some embodiments, the thinning processis performed by a mechanical grinding process, a chemical mechanicalpolish (CMP), some other thinning process, or any combination of theforegoing. For example, the thinning process may be performed wholly bya mechanical grinding process.

As shown in cross-sectional view 2700 of FIG. 27, the adhesive bondinglayer (2302 of FIG. 26) and the sacrificial substrate (2304 of FIG. 26)are separated from the MEMS device structure 102 (de-bond from ILDstructure 120). After the separation process, a lower masking layer 802is formed on a bottom surface of the carrier substrate 103 and an uppermasking layer 804 is formed over the ILD structure 120. In someembodiments, the lower masking layer 802 and/or the upper masking layer804 may, for example, respectively be or comprise a photoresist, a hardmask layer, or the like. The lower masking layer 802 and the uppermasking layer 804 respectively have a plurality of sidewalls defining aplurality of openings.

As shown in cross-sectional view 2800 of FIG. 28, a first patterningprocess is performed on the carrier substrate 103 according to the lowermasking layer 802. In some embodiments, the first patterning processincludes performing a dry etching process, such as a plasma etchingprocess and/or a deep reactive-ion etching (DRIE) process. The firstpatterning process defines the carrier substrate opening 101 directlyunderlying the particle filter 106.

Also as shown in FIG. 28, after the first patterning process, a secondpatterning process is performed on the carrier substrate 103 and theMEMS substrate 111 according to the lower masking layer 802. In someembodiments, the second patterning process includes performing a wetetching process, such as an isotropic etching process and/or a dryetching process. The second patterning process may include exposing thecarrier substrate 103 and/or the MEMS substrate 111 to one or moreetchants, such as, for example, xenon difluoride (XeF2). The secondpatterning process removes the plurality of pillars (2402 of FIG. 27)and may expand a width of the carrier substrate opening 101.

As shown in cross-sectional view 2900 of FIG. 29, a third patterningprocess is performed on the structure of FIG. 28. In some embodiments,the third patterning process includes performing a wet etching processand exposing the structure of FIG. 28 to one or more etchants. The thirdpatterning removes a portion of the ILD structure 120, thereby definingthe air volume space 113. Further, the fourth patterning process removesthe lower dielectric layer 104 a from a bottom surface of the particlefilter 106 and removes the upper dielectric layer 104 c from a topsurface of the particle filter 106. After performing the thirdpatterning process, a removal process is performed to remove the lowerand upper masking layers (802, 804 of FIG. 28).

FIG. 30 illustrates a third method 3000 of forming a MEMS microphonewith a particle filter in accordance with some embodiments. Although thethird method 3000 is illustrated and/or described as a series of acts orevents, it will be appreciated that the method is not limited to theillustrated ordering or acts. Thus, in some embodiments, the acts may becarried out in different orders than illustrated, and/or may be carriedout concurrently. Further, in some embodiments, the illustrated acts orevents may be subdivided into multiple acts or events, which may becarried out at separate times or concurrently with other acts orsub-acts. In some embodiments, some illustrated acts or events may beomitted, and other un-illustrated acts or events may be included.

At act 3002, a MEMS substrate is provided. FIG. 22 illustrates across-sectional view 2200 corresponding to some embodiments of act 3002.

At act 3004, a MEMS structure is formed over the MEMS substrate. TheMEMS structure includes a first back plate, a second back plate, and adiaphragm disposed between the first and second back plates. FIG. 22illustrates a cross-sectional view 2200 corresponding to someembodiments of act 3004.

At act 3006, a sacrificial substrate is bonded to the MEMS structure.FIG. 23 illustrates a cross-sectional view 2300 corresponding to someembodiments of act 3006.

At act 3008, an etching process is performed on the MEMS substrate,thereby defining a plurality of pillars in the MEMS substrate. FIG. 24illustrates a cross-sectional view 2400 corresponding to someembodiments of act 3008.

At act 3010, a carrier substrate is provided and a filter stack isformed over the carrier substrate. The filter stack includes an upperdielectric layer, a particle filter layer, and a lower dielectric layer,the particle filter layer is disposed between the upper and lowerdielectric layers. FIG. 25 illustrates a cross-sectional view 2500corresponding to some embodiments of act 3010.

At act 3012, an etching process is performed on the filter stack,thereby defining a particle filter in the particle filter layer. FIG. 25illustrates a cross-sectional view 2500 corresponding to someembodiments of act 3012.

At act 3014, the MEMS substrate is bonded to the filter stack. FIG. 26illustrates a cross-sectional view 2600 corresponding to someembodiments of act 3014.

At act 3016, a thinning process is performed on the carrier substrate.After the thinning process, the sacrificial substrate is de-bonded fromthe MEMS structure. FIG. 27 illustrates a cross-sectional view 2700corresponding to some embodiments of act 3016.

At act 3018, a dry etching process is performed on the carriersubstrate, thereby defining an opening in the carrier substrate directlybelow the particle filter. FIG. 28 illustrates a cross-sectional view2800 corresponding to some embodiments of act 3018.

At act 3020, a wet etching process is performed on the MEMS substrate,thereby removing the plurality of pillars. FIG. 28 illustrates across-sectional view 2800 corresponding to some embodiments of act 3020.

At act 3022, an etching process is performed on the MEMS substrate andthe filter stack, thereby defining an air volume space around the firstback plate, second back plate, and the diaphragm. The etching processremoves the upper and lower dielectric layers from the particle filter.FIG. 29 illustrates a cross-sectional view 2900 corresponding to someembodiments of act 3022.

Accordingly, in some embodiments, the present disclosure relates tomultiple methods that simplify the fabrication of a MEMS device with aparticle filter, such that the particle filter is disposed between aMEMS substrate and a carrier substrate.

In some embodiments, the present application provides a microphoneincluding a microelectromechanical systems (MEMS) device structureoverlying a MEMS substrate, wherein the MEMS device structure includes adiaphragm having opposing sidewalls that define a diaphragm opening; acarrier substrate underlying the MEMS substrate, wherein the carriersubstrate has opposing sidewalls that define a carrier substrate openingunderlying the diaphragm opening; and a filter stack sandwiched betweenthe carrier substrate and the MEMS substrate, the filter stack includesan upper dielectric layer, a lower dielectric layer, and a particlefilter layer disposed between the upper and lower dielectric layers,wherein the particle filter layer includes a particle filter spacedlaterally between the opposing sidewalls of the carrier substrate.

In some embodiments, the present application provides amicroelectromechanical systems (MEMS) device, including a MEMS substratehaving opposing sidewalls that define a MEMS opening; a MEMS structurevertically over the MEMS substrate, wherein the MEMS structure includesa first back plate and a diaphragm vertically separated from the firstback plate; a carrier substrate underlying the MEMS substrate, whereinthe carrier substrate has opposing sidewalls defining a carriersubstrate opening, wherein the carrier substrate opening underlies thediaphragm and the MEMS opening; and a filter stack disposed between thecarrier substrate and the MEMS substrate, wherein the filter stackincludes a particle filter layer having a particle filter, wherein theparticle filter includes a plurality of filter openings that extendsthrough the particle filter layer and is laterally between the opposingsidewalls of the MEMS substrate.

In some embodiments, the present application provides a method formanufacturing a microelectromechanical systems (MEMS) device, the methodincludes forming a filter stack over a carrier substrate, wherein thefilter stack includes an upper dielectric layer, a lower dielectriclayer, and a particle filter layer disposed between the upper and lowerdielectric layers; patterning the filter stack to define a particlefilter in the particle filter layer, the particle filter having one ormore surfaces continuously extending around a plurality of filteropenings; bonding a MEMS substrate to the upper dielectric layer;forming a MEMS structure over the MEMS substrate, the MEMS structureincludes a mobile diaphragm; patterning the carrier substrate to definea carrier substrate opening in the carrier substrate; patterning theMEMS substrate to define a MEMS opening in the MEMS substrate; andperforming an etch process on the MEMS structure and the filter stack,wherein the etch process removes the upper and lower dielectric layersfrom directly above and directly below the particle filter.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

1. A microphone comprising: a microelectromechanical systems (MEMS) device structure overlying a MEMS substrate, wherein the MEMS device structure includes a diaphragm having opposing sidewalls that define a diaphragm opening; a carrier substrate underlying the MEMS substrate, wherein the carrier substrate has opposing sidewalls that define a carrier substrate opening underlying the diaphragm opening; and a filter stack sandwiched between the carrier substrate and the MEMS substrate, the filter stack includes an upper dielectric layer, a lower dielectric layer, and a particle filter layer disposed between the upper and lower dielectric layers, wherein the particle filter layer comprises a particle filter spaced laterally between the opposing sidewalls of the carrier substrate, and wherein the particle filter layer includes an upper filter layer, a lower filter layer, and a middle filter layer disposed between the upper and lower filter layers, wherein the upper and lower filter layers comprise a first material, and wherein the middle filter layer comprises a second material different from the first material.
 2. The microphone of claim 1, wherein the particle filter has a plurality of opposing sidewalls that define a plurality of filter openings, wherein the plurality of filter openings are laterally between the opposing sidewalls of the carrier substrate, and wherein the particle filter layer includes a polysilicon layer sandwiched between an upper silicon nitride layer and a lower silicon nitride layer.
 3. The microphone of claim 2, wherein the particle filter layer comprises silicon nitride, and wherein the upper and lower dielectric layers each comprise an oxide.
 4. The microphone of claim 2, wherein the first material comprises silicon nitride and the second material comprises polysilicon.
 5. The microphone of claim 2, wherein a thickness of the particle filter layer is less than a thickness of the upper dielectric layer and less than a thickness of the lower dielectric layer.
 6. (canceled)
 7. (canceled)
 8. The microphone of claim 1, wherein a thickness of the MEMS substrate is less than a thickness of the carrier substrate.
 9. A microelectromechanical systems (MEMS) device, comprising: a MEMS substrate having opposing sidewalls that define a MEMS opening; a MEMS structure vertically over the MEMS substrate, wherein the MEMS structure includes a first back plate and a diaphragm vertically separated from the first back plate; a carrier substrate underlying the MEMS substrate, wherein the carrier substrate has opposing sidewalls defining a carrier substrate opening, wherein the carrier substrate opening underlies the diaphragm and the MEMS opening; and a filter stack disposed between the carrier substrate and the MEMS substrate, wherein the filter stack includes a particle filter layer having a particle filter, wherein the particle filter comprises a plurality of filter openings that extends through the particle filter layer and is laterally between the opposing sidewalls of the MEMS substrate, wherein the particle filter layer includes a polysilicon layer, a first nitride layer, and a second nitride layer, wherein the plurality of filter openings of the particle filter are defined by sidewalls of the first nitride layer, sidewalls of the second nitride layer, and sidewalls of the polysilicon layer disposed between the first and second nitride layers.
 10. The MEMS device of claim 9, wherein the filter stack further includes: an upper dielectric layer disposed between the MEMS substrate and the particle filter layer; a lower dielectric layer disposed between the carrier substrate and the particle filter layer; and wherein outer sidewalls of the particle filter layer extend past outer sidewalls of the upper dielectric layer and outer sidewalls of the lower dielectric layer.
 11. The MEMS device of claim 10, wherein the outer sidewalls of the upper dielectric layer and the outer sidewalls of the lower dielectric layer are respectively laterally offset from the outer sidewalls of the particle filter layer by a non-zero distance in a direction towards the plurality of filter openings.
 12. The MEMS device of claim 10, wherein the upper and lower dielectric layers each comprise an oxide.
 13. (canceled)
 14. The MEMS device of claim 9, wherein a thickness of the particle filter layer is less than a thickness of the MEMS substrate, wherein a thickness of the MEMS substrate is less than a thickness of the carrier substrate.
 15. The MEMS device of claim 9, wherein the carrier substrate comprises sidewalls defining a carrier substrate opening beneath the particle filter.
 16. The MEMS device of claim 9, wherein the plurality of filter openings are circular or elliptical when viewed from above.
 17. A method for manufacturing a microelectromechanical systems (MEMS) device, the method comprising: forming a filter stack over a carrier substrate, wherein the filter stack includes an upper dielectric layer, a lower dielectric layer, and a particle filter layer disposed between the upper and lower dielectric layers; patterning the filter stack while the filter stack is disposed on the carrier substrate to define a particle filter in the particle filter layer, wherein the particle filter has one or more surfaces continuously extending around a plurality of filter openings; bonding a MEMS substrate to the upper dielectric layer; forming a MEMS structure over the MEMS substrate, the MEMS structure includes a mobile diaphragm; patterning the carrier substrate to define a carrier substrate opening in the carrier substrate; patterning the MEMS substrate to define a MEMS opening in the MEMS substrate; and performing an etch process on the MEMS structure and the filter stack, wherein the etch process removes the upper and lower dielectric layers from directly above and directly below the particle filter.
 18. The method according to claim 17, wherein the filter stack is patterned before bonding the MEMS substrate to the upper dielectric layer.
 19. The method according to claim 17, wherein the filter stack is patterned after defining the carrier substrate opening and before defining the MEMS opening in the MEMS substrate.
 20. The method according to claim 17, wherein the MEMS structure is formed over the MEMS substrate before bonding the MEMS substrate to the upper dielectric layer.
 21. The method according to claim 17, wherein the MEMS structure further comprises a first back plate and a second back plate, and wherein the particle filter layer includes an upper filter layer, a lower filter layer, and a middle filter layer disposed between the upper and lower filter layers, wherein the upper and lower filter layers comprise silicon nitride, and wherein the middle filter layer comprises polysilicon.
 22. The method according to claim 17, wherein patterning the filter stack includes removing segments of the upper dielectric layer, segments of the lower dielectric layer, and segments of the particle filter layer.
 23. The method according to claim 17, further comprising: performing a dry etching process on the MEMS substrate to define pillars in the MEMS substrate before patterning the MEMS substrate. 